function difference1(arry1,arry2=[undefined]){
  arr1 = arry1.sort(function(a,b){
    return a-b
  })
  arr2 = arry2.sort(function(a,b){
    return a-b
  })
  arr1ponter=arr2ponter = 0
  res = []
  if(arr2[arr2.length-1] < arr1[0]){
    return arry1,slice()
  }
  while (arr1ponter < arr1.length && arr2ponter <arr2.length){
      if(arr1[arr1ponter]===arr2[arr2ponter]){
        arr1ponter+= 1
        arr2ponter+= 1
        continue
      }else{
        res.push(arr1[arr1ponter])
      }
      arr1ponter += 1
  }
  res.push(...arr1.slice(arr1ponter+1,arr1.length))
  return res
}
function difference2(arry1,arry2=[]){
  if(arry1.length === 0){
    return []
  }
  if(arry2.length ===0){
    return arry1.slice()
  }
  const res = arry1.filter(item => !arry2.includes(item))
  return res
}